Gypsy Moth – Lymantria dispar

Gypsy Moth – Lymantria dispar
Family: Erebidae
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Live larvae and adults photographed at Illinois and Pennsylvania, USA
Gypsy moth male
These huge, active moths are, unfortunately, quite numerous in the forests around Marienville, Pennsylvania. Diurnal moths with quick, erratic, darting flight, the gypsy moths are quite "friendly", always seeming to get into the car, the tent, all sorts of enclosed spaces. I don't know if they are attracted to my carbon dioxide or what, but at times they became bothersome.

A newly introduced variant, the Asian gypsy moth (AGM, including Lymantria dispar asiatica, Lymantria dispar japonica, Lymantria albescens, Lymantria umbrosa, and Lymantria postalba) is an exotic pest not known to occur naturally in the United States.

AGM was first identified in North America late in 1991 near the Port of Vancouver in British Columbia, Canada. Moths were discovered in Washington, Oregon, and British Columbia shortly after that. Ships infested with egg masses from ports in eastern Russia probably introduced the pest to North America while visiting ports on the West Coast. Scientists believe that while the ships were docked, larvae hatched from the eggs and were blown ashore.

APHIS and State officials eradicated that infestation in the Pacific Northwest through trapping and spraying activities. Another AGM infestation, this one in Sunny Point, NC, was caused by moths emerging from a ship carrying infested cargo containers from Germany. AGM was not known to occur in Europe until tracebacks of this introduction led the U.S. Department of Agriculture (USDA) there. The North Carolina infestation was declared eradicated in November 1997. Also in 1997, AGM was again detected in the Seattle–Tacoma, WA, area. The joint Federal and State eradication program ended in 1999.

Each AGM female could lay egg masses that in turn could yield hundreds of voracious caterpillars with appetites for more than 500 species of trees and shrubs. AGM defoliation would severely weaken trees and shrubs, killing them or making them susceptible to diseases and other pests. Caterpillar silk strands, droppings, destroyed leaves, and dead moths would be a nuisance in homes, yards, and parks. A risk assessment prepared by the USDA’s Animal and Plant Health Inspection Service (APHIS) and the USDA’s Forest Service concluded that because of similarities between Asian and North American ecosystems, the AGM has great potential for colonization in North American forests. [1]

Gypsy Moth

Life Stages: The AGM matures through four life stages: egg, larva (caterpillar), pupae (cocoon), and moth. AGM egg masses may be found on trees, stones, walls, logs, lawn furniture, and other outdoor objects. Each egg mass can contain more than 1,000 eggs. The mass is covered with buff or yellowish fuzz from the abdomen of the female. While the velvety egg masses average about 1–1/2 inches long and about 3/4 of an inch wide, they are often as small as a dime.

AGM eggs begin hatching into caterpillars in the spring. All of the damage caused by the AGM is done during the caterpillar stage, as the insects feed on leaves during this active period of growth. AGM caterpillars stop feeding when they enter the pupal or cocoon stage. This stage begins in June or July, depending on weather and temperature. Adult moths emerge from the dark brown pupal cases in 10 to 14 days. Adult males have grayish-brown wings and a wingspan of 1–1/2 inches. Adult female moths are white and larger, with wingspans up to 3–1/2 inches or more.

AGM’s do not feed in the moth stage (which lasts 1 to 3 weeks) but only mate and lay eggs. Eggs are laid between July and September, depending on weather and location. The eggs remain dormant during winter and and hatch the following spring. [1]

Gypsy Moth Caterpillar
AGM Caterpillar
Spread of Infestations: AGM infestations spread in several ways. Adult female moths may fly to previously uninfested areas to lay eggs, thus spreading the infestation. Or, newly hatched AGM caterpillars may climb to tree crowns, where the wind picks up their silken thread and carries them to other areas. In addition, people can inadvertently transport egg masses. AGM egg masses are tolerant of extremes in temperature and moisture and travel well on logs, lawn furniture, nursery stock, pallets, shipping containers, and on the hulls and riggings of ships.

The most common eradication method used against AGM is the naturally occurring Bacillus thuringiensis (Bt) bacteria. Bt produces a caterpillar–specific toxin. When sprayed on tree leaves, Bt will disrupt the digestive system of caterpillars that ingest the leaves, suppressing their appetites. The caterpillars' movement then slows, and death results, generally in 7 to 10 days.

People can take several actions to assist in the detection and management of this pest:

  • Report any findings of egg masses on trees, lawn furniture, fences, walls, or elsewhere to State agriculture officials.
  • Cooperate with any restrictions that might be imposed locally because of an AGM detection.
  • Allow authorized agriculture workers access to property to inspect insect–monitoring traps.

    1. USDA, Animal and Plant Health Inspection Service (APHIS), Fact Sheet "Asian Gypsy Moth"

Gypsy Moth - Lymantria dispar

Order Lepidoptera: Moths. Unlike the butterflies, moths are usually nocturnal. Many moths and their caterpillars are major agricultural pests in large parts of the world. Moths in the family Tineidae are commonly regarded as pests because their larvae eat fabrics, clothes and blankets made from natural fibers such as wool or silk. Moths in the genus Farinalis feed on stored grain, flour, corn meal and other milled grain products.
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